If we look closely into the grass here on the slope of the fosse it is animated by a busy throng of insects rushing in hot haste to and fro. They must find it a labour and a toil to make progress through the green forest of grass-blade and moss and heaths and thick thyme bunches, over-topping them as cedars, but cedars all strewn in confusion, crossing and interlacing, with no path through the jungle. Watch this ant travelling patiently onward, and mark the distance traversed by the milestone of a tall bennet.
First up on a dry white stalk of grass lingering from last autumn; then down on to a thistle leaf, round it, and along a bent blade leading beneath into the intricacy and darkness at the roots. Presently, after a prolonged absence, up again on a dead fibre of grass, brown and withered, torn up by the sheep but not eaten: this lies like a bridge across a yawning chasm—the mark or indentation left by the hoof of a horse scrambling up when the turf was wet and soft. Half-way across the weight of the ant overbalances it, slight as that weight is, and down it goes into the cavity: undaunted, after getting clear, the insect begins to climb up the precipitous edge and again plunges into the wood. Coming to a broader leaf, which promises an open space, it is found to be hairy, and therefore impassable except with infinite trouble; so the wayfarer endeavours to pass underneath, but has in the end to work round it. Then a breadth of moss intervenes, which is worse than the vast prickly hedges with which savage kings fence their cities to the explorer, who can get no certain footing on it, but falls through and climbs up again twenty times, and burrows a way somehow in the shady depths below.
Next, a bunch of thyme crosses the path: and here for a lengthened period the ant goes utterly out of sight, lost in the interior, slowly groping round about within, and finally emerging in a glade where your walking-stick, carelessly thrown on the ground, bends back the grass and so throws open a lane to the traveller. In a straight line the distance thus painfully traversed may be ten or twelve inches; certainly in getting over it the insect has covered not less than three times as much, probably more—now up, now down, backwards and sideways, searching out a passage.
As this process goes on from morn till night through the long summer’s day, some faint idea may be obtained of the journeys thus performed, against difficulties and obstacles before which the task of crossing Africa from sea to sea is a trifle. How, for instance, does the ant manage to keep a tolerably correct course, steering straight despite the turns and labyrinthine involutions of the path? It is never possible to see far in front—half the time not twice its own length; often and often it is necessary to retrace the trail and strike out a fresh one—a step that would confuse most persons even in an English wood with which they were unacquainted.
Yet by some power of observation, perhaps superior in this respect to the abilities of greater creatures, the tiny thing guides its footsteps without faltering down yonder to the nest in the hollow on the bank of the ploughed field. I say by observation, and the exercise of faculties resembling those of the mind, because I have many times tried the supposed unerring instinct of the ant, and found it fail: therefore it must possess a power of correcting error which is the prerogative of reason. Ants cannot, under certain conditions, distinguish their own special haunts. Across a garden path I frequented there was the track of innumerable ants; their ceaseless journeyings had worn a visible path leading from the border on one side to the border on the other, where was a tiny hole, into which they each disappeared in turn. Happily, the garden was neglected, otherwise the besom of the gardener would have swept away all traces of the highway they had made. Watching the stream of life pouring swiftly along the track, it seemed to me that, like men walking hurriedly in well-known streets, they took no note of marks or bearings, but followed each other unhesitatingly in the groove.
When street-pavements are torn up, the human stream disperses and flows out on either side till it discovers by experience the most convenient makeshift passage. What would be the result if this Watling-street of the ants were interrupted? With a fragment of wood I rubbed out three inches of the path worn in the shallow film of soil deposited over the old gravel, smoothing that much down level. Instantly the crowd came to a stop. The foremost ant halted at the edge where the groove now terminated, turned round, and had an excited conversation with the next by means of their antennae; a third came up, a fourth and fifth—a crowd collected, in fact. Now, there was no real obstruction—nothing to prevent them from rushing across to the spot where the path recommenced. Why, then, did they pause? Why, presently, begin to explore, right and left, darting to one side and then to the other examining? Was it not because an old and acquired habit was suddenly uprooted? Surely infallible instinct could have carried them across the space of three inches without any trouble of investigation?
In a few seconds one of the exploring parties, making a curve, hit the other end of the path, and the news was quickly spread, for the rest followed almost immediately. Placing a small pebble across the track on another occasion caused almost the same amount of interference with the traffic. Near the hole into which the ants plunged under the border, and on the edge of the bank, so to say, the path they had worn was not visible—the ground was hard and did not take impression; and there, losing the guidance of the groove, they often made mistakes. Instead of hitting the right hole, many of them missed it and entered other holes left by boring worms, and after a short time reappeared to search again, till, finding the cavern, they hastily plunged into it. This was particularly the case when a solitary insect came along. Therefore it would seem that the ant works its way tentatively, and, observing where it fails, tries another place and succeeds.